Weft insertion warp knitting machines are often utilized for the production of dimensionally stable fabrics, particularly for the production of draperies or upholstery. Typically, the weft yarns are held on a substrate utilizing a chain stitch or tricot stitch knitting construction. A single stitch forming guide bar is utilized to pattern the stitching to achieve the desired dimensionally stable chain or tricot stitch construction. The stitch construction is dimensionally stable because it ties the weft yarn down at regular intervals in a basically rectilinear way. While the product produced does thus have the desired feature of dimensional stability, often the fabric is stiff, and has poor aesthetic qualitities compared to similar woven fabrics.
For cost and efficiency reasons, conventional drapery fabrics are usually produced utilizing a 150 denier textured polyester stitching yarn, which is natural in color. The stitching yarn is highly visible in the final fabric (especially where medium to dark colored weft or decorative warp yarns are utilized), resulting in an undesirable appearance. Efforts have therefore been made to improve the appearance by covering the warp yarns with dyed yarn, utilizing irregular threading of the stitching yarn, etc. However such attempts have not been uniformly successful, and the final fabric produced typically is not entirely aesthetically acceptable.
According to the present invention, a dimensionally stable fabric is produced that is more asethetically pleasing. This is accomplished according to the present invention basically by utilizing two stitch forming guide bars in the weft inserted warp knitting machine, and moving the stitching bars in opposite directions in basically a zigzag form. While this stitch combination is dimensionally unstable (especially in fabric constructions with under 18 needles lined and/or under 18 courses per inch) since it does not tie the weft yarn down in regular mostly rectilinear intervals, and thus typically has not been thought suitable for drapery or upholstery fabric, in view of the fact that a dimensionally stable substrate is utilized (such as a 100 percent polyester nonwoven fabric), a dimensionally stable fabric does ensue. The appearance of the fabric is greatly improved vis-a-vis conventional drapery fabrics having chain stitch or tricot stitch configurations, and even though 150 denier textured polyester stitching yarn is also visible in the fabrics according to the invention, when knitted together with medium to dark colored weft yarns, it presents a less detrimental appearance because it becomes part of the design.
According to an exemplary method of the present invention, a decorative fabric is produced utilizing a weft inserted warp knitting machine having two or more stitching bars. The method comprises the following steps: (a) feeding a warp-wise stable substrate in a direction A to the knitting machine; (b) inserting weft yarn in a direction perpendicular to direction A utilizing the knitting machine; (c) feeding stitching thread to the stitching bars; (d) while stitching with the stitching bars, to cause the stitching thread to hold the weft yarn in place on the substrate, moving the stitching bars in opposite directions in a basically zigzag form to create an as such dimensionallly unstable, but aesthetic, pattern of stitching formation in the fabric produced; (e) finishing the fabric produced by steps (a)-(d); and (f) cutting the finished fabric to form desired fabric pieces.
It has been found, according to the present invention, that the stitching yarn must be very loose when fed to the stitching bars, otherwise the fabric is pulled in and an unacceptable product results. Therefore according to the present invention step (c) is practiced by utilizing feed rollers driven at a constant speed, or a like structure, for positive feeding of the stitching yarn to the stitching bars to make sure that there is not too much tension.
It has also been found according to the present invention that the fabric produced has a tendency to fold or curl at the edges as it comes off the knitting machine. This folding or curling creates problems during finishing operations since the fabric is pulled through the finishing structures for foam coating, or the application of other finishes, by exerting tension on the fabric. In order to ensure that the fabric can be finished properly, according to the invention it is desirable to provide a third stitching bar which stitches the selvage areas of the fabric (approximately a one inch selvage on either side of a central body portion of the fabric being provided) with a dimensionally stable stitching configuration, particularly chain stitching.
Thus, according to the invention an intermediate fabric, for the production of a decorative final fabric, is produced. The intermediate fabric according to the invention comprises: a warp-wise dimensionally stable substrate having a first face; weft yarns disposed on the first face of the substrate and extending parallel to each other; stitching thread for holding the weft yarns on the first face; the stitching thread comprising in a central body section of the fabric, between opposite ends thereof in a dimension basically perpendicular to the machine direction, stitching thread disposed in a dimensionally unstable, but aesthetic, configuration; and said stitching thread in selvage edge portions of the fabric, on opposite sides of the central body section thereof, stitching thread disposed in a dimensionally stable configuration. Decorative warp yarns also may be utilized, with the stitching holding the decorative warp yarns in place. The decorative warp yarns typically need not be applied in the selvage area.
Also according to the present invention, an upholstery or drapery or other dimensionally stable fabric is produced (i.e. a fabric that has sufficient dimensional stability) which also has excellent aesthetic properties compared to such fabrics typically produced on weft inserted warp knitting machines, Malimo machines, and the like. The fabric according to the invention comprises: a warp-wise stable substrate having a first face; weft yarns disposed on the first face of the substrate, and extending parallel to each other; and stitching thread in a dimensionally unstable, but aesthetic, pattern, holding the weft yarns in place on the substrate. Typically a foam backing will be provided on a second face of the fabric, opposite the first face, and decorative warp yarns will be utilized on the first face on top of the weft yarns.
It is the primary object of the present invention to provide a method for the production of, and to produce, a decorative fabric, useful for drapery and upholstery functions, which has good aesthetic properties. This and other objects of the invention will become clear from an inspection of the detailed description of the invention, and from the appended claims.